Process of making lime



Nov. 2, 1937. F HORTON 2,097,979

PROCESS OF MAKING LIME Filed Jan. 13, 1936 24 amen o0 Ggozye I #077572,

Patented Nov. 2, 1937 g UNITED STATES PATENT OFFICE Y Ainflicatl o zu fylt ligwriil 1; 58,964 2 Claims. (01. 203-53) This invention relates toan improved processv danger of oven-burning such small particles. In ofproducing lime by the calcining of oyster accordance with my process,the shells and small shells and the like. i particles thereof are simplywashed to remove Heretofore, in the production of lime from therefromthe dirt or impurities which usually 6 oyster shells and the like, ithas been customary accompany the same when removed in comto crush theoyster shells or the like and theremercial supplies by mechanical"dredging appaafter burn the crushed shells or the like in a conratusfrom reefs. The washed shells and small ventional rotary kiln embodyinga cylinder inparticles may then be-calcined, or they may first clinedfrom one end to the other and rotatable be fed toa suitable crusher orcrushing rollers 10 to agitate the pieces of shell or the like and so asto reduce them to pieces of desired sizes 10 continuously convey themthroughthe kiln durand other relatively smaller particles, If the ingthe burning process, the burning being acshells are crushed, they may bescreened to limit complished by the direct action of a flame on 'the themaximum size thereof, the pieces smaller pieces of shell or the like,which flame is prothan a given size together with the smaller par- 1jected into the cylinder of the kiln substantially ticles being suppliedin batches to a rotary kiln from one end thereof to the other. Due tothis in which the shells are subjected to a roasting actual burningoperation by the direct action of heat devoid of direct contact withaflame or a-flame on the pieces of shell or the like, it has with hotsurfaces capable of burning the shells been necessary to screen and washthe crushed and small particles thereof. In this way, the

shells to eliminate or remove the small particles calcining of theshells is accomplished by a, roast- 2 which would otherwise be passed tothe kiln and ing operation as distinguished from a burning beover-burned during the calcining operation. operation, and the roastingoperation is contin- Obviously, the inability to make use of the smallued for a proper period of time while controlling particles of crushedshell results in the waste the heat to'avoid excessive temperatures, sothat of an enormous quantity of material from which over-burning of thefine or small particles of 25 lime could be produced if over-burningthereof shells is prevented, particularly as the shells are could beprevented. continuously agitated during the roasting oper- The primaryobject of the present invention, ation. If the shells are crushed, thepieces theretherefore, is to provide an improved process of of above thementioned maximum size may be making lime from oyster shells or thelike, returned to-the crusher or crushing rolls so as 30 whereby thesmall particles of shells may be calto be properly reduced to therequired extent. cined along with the larger pieces thereof with-Obviously, my process avoids the necessity of out danger of over-burningsuch small particles, washing'and screeningthe shells before thecalthereby making use of these small or finer parcining operation toeliminate or remove the small ticles which are ordinarily wasted, andrenderparticles of shells, and makes it possible to make 35 ingitunnecessary to screen and wash the crushed use of such small particleswhich are ordinarily shells toeliminate the small particles or removewasted because of the danger of over-burning the the latter from thelarger pieces of shells before same in apparatus and by processesheretofore heating the latter in a kiln to calcine them or employed.

40 convert them from carbonates to oxides. I ac- Other objects of theinvention will be appar- 40 complish this object primarily by subjectingthe ent to those skilled in the art, when the followwashed reef-runshells or crushed shells, from ing description is considered inconnection with. which the small shell particles have not been theaccompanying drawing, wherein: eliminated, to the action of heat by aroasting Figure 1 is a diagrammatic elevational view iloperation asdistinguished from the direct action lustrating one form of apparatussuitable for 45 of a flame or a burning operation. As my processcarrying out certain steps that may be included excludes the usualburning operation or the in the present process; and usual direct actionof a flame on the crushed Figure 2 is a somewhat similar view, drawn onshells, over-burning of the small particles is -a larger scale, showingthe apparatus for roastrendered highly unlikely,the degree of heat beingthe shells and smallparticles thereof to cal- 50 ing properly controlledso as to not be excessive, cine them, after subjecting them to thewashand the roasting operation being prolonged for ing operation, or tothe washing, crushing and a sufficient periodof time andwhilecontinuously screening operations performed by the apparatusagitating the shells and small particles thereof illustrated in Figure1.

to insure thorough calcining of the same without Commercial Suppli s 01M 1 Shells m in reefs and are usually removed by mechanical dredgingequipment. Such removal obviously picks up small particles of shells anddirt and other impurities which have accumulated with the shells. Inpracticing the present invention, it is essential that this dirt andthese impurities be substantially removed from the shells and particlesthereof. Therefore, as shown in Figure 1, the shells and shell particlesare delivered to a washer generally indicated at 5, as by means of aconveyor ii and chute 1. After the shells and smail'particles thereofhave been cleanedby the washer 5, they may be calcined, or they mayfirst be passed to a crusher or crushing rolls 8 so as to be reduced topieces of suitable size for calcining. Any; suitable means such as aconveyor 9 and chutes l and ii may be provided for conveying the shellsfrom the washer i to the crushing rolls 8. The crushing rolls 8 not onlyreduce the shells to pieces of suitable size for calcining,but alsobreak the shells into considerable other small particles which mustordinarily be removed or eliminated because of danger clover-burning thesame when calcined in accordance with prior processes by the use of anordinary rotary kiln in which the crushed shells are subjected to thedirect action of a flame for burning. From the crushing rolls 8, thecrushed shells may be conveyed by a chute ii to a suitable screeningdevice it for limiting the maximum size of the pieces of shell collectedfor the calcining operation. The pieces smaller than a given size,together with the small particles, pass through thisscreening device andmay be collected in a suitable receptacle it for use in making lime. Aconveyor i and chute l6 may deliver these pieces and small particles ofshell from the screening device l3 to the receptacle M. Any piece ofshell larger than the mentioned maximum size may be returned to thecrushing rolls 8 for being further crushed and thereby reduced to usablesizes. This may be accomplished by means of a chute 1'! arranged todeliver the pieces of greater than desirable size to an elevator itwhich in turn discharges onto a chute I9, the chute l9 conveying thepieces of shell to a conveyor 20 that in turn discharges onto a chute 2|arranged to direct the shells back between the crushing rolls 8.

While a particular diagrammatic arrangement of apparatus has beenillustrated in Figure 1,

- it is to be understood that the same is merely illustrative and thatwidely different apparatus may be used. The essential purpose of-Figurel is to show that, in accordance with the present process, the shellsare first washed or cleaned,

after which they may be crushed and 'then cleaned so that the piecessmaller than a given size and the still smaller particles are collectedfor use in the production of lime, any pieces larger than a given sizebeing crushed again to smaller size before they are collected and usedin the production of lime. It will be noted, however, thatthe smallparticles are not removed or eliminated, but are collected with thelarger pieces of proper size or of smaller than a given mas-durum size,forbeing calcined.

The shells or pieces of crushed shells, together with the accompanyingsmall particles, collected in the receptacle it, are then subjected to aroasting operation for being converted from carbonates to oxides, suchroasting operation being accomplished by subjecting the crushed shellsto the action oi heat while agitating the same, as

rlhting'aished from subjecting them to the bumfiled June 24, 1935.

aoevpve ing action oi a flame. This roasting operation is preferablyaccomplished by means of a kiln of the type disclosed in my co-pendingapplication for U. S. Letters Patent Serial Number 28,179 AS broadlyillustrated in Figure 2, this kiln includes a. roasting drum 22 having aremovable closure 23 to facilitate the introduction of batches of cleanshells or crushed shells and small particles into the same or dis-'charge of the lime therefrom. The shells in the drum 22 are roasted bysubjecting them to heat without bringing them in direct contact with aflame or hot surfaces capable of burning the shells. In other words, theshells are not actually burned, but are merely highly heated and therebyroasted. By properly regulating this heat while agitating the shells andsubjecting them to the heating operation for a properly prolonged periodof time, the desired calcining operation is accomplished. One manner ofroasting the shells is to supply a heating medium to the drum 2!, or todischarge hot products of combustion thereto and simultaneously permitcontrolled escape of the hot products of combustion from the drum 22.This may be accomplished by producing the products of combustion in aseparate furnace 24 and conveying the products of combustion from thisfurnace to the drum 22 by means of a pipe 25 which opens into one end ofdrum 22, the hot products of combustion being allowed to escape from theopposite end of drum 22 by means of a discharge pipe 28 having a controlvalve 2'! to regulate such escape of the products of combustion.Suitable means as generally indicated at 28 will of course be providedfor continuously rotating the drum 22 during each roasting operation, soas to continuously agitate the shells while being roasted. In this way,the shells may be uniformly heated and roasted so that a uniform productwill be obtained in which not even the small particles of shells will beoverburned or over-roasted. The furnace 24 is preferably of the typeemploying a. gas burner for producing the hot products of combustionused in the calcining operation, thus providing for the production ofproducts of combustion having no residue to contaminate the product ofthe calcining operation.

In view of the above, it will be seen that I have provided a very simpleand inexpensive process for the production of a good quality of lime,and whereby the small particles of shells may be utilized without beingover-burned. By controlling the escape of the hot products of combustionfrom the kiln as explained herein, I prevent thecreation of a strongdraft through the kiln so that the very fine particles of shell do notform suspended dust to interfere with the calcining operation and arenot carried oh and lost or wasted, as would be the case if the escape ofthe products of combustion were not controlled or restricted. While theinvention has been described as applied to oyster shells, it is intendedthat the invention be understood as applicable to other equivalentmaterial, particularly to clam and other types of marine shells.

What I claim as new is:

1. A process of making lime from pieces and smaller particles of crushedoyster shells consistlng of roasting successive batches of the piecesand smaller particles of shells in a rotary kiln by the controlledapplication of heat at calcining temperatures and so as to exclude saidpieces andsmaller particles of shells from contact with a flame or hotsurfaces capable of burning them, during rotation of the kiln andagitation of said pieces and smaller particles.

2. A process of making lime from oyster shells and the like, includingpassing the shells through kiln by supplying hot products of combustiondevoid of flame to said kiln from an external source and controllingonly the escape of said hot products of combustion from said kiln tomaintain the desired calcining temperatures within the kiln duringrotation of the latter and agitation of the pieces and particles ofshells being roasted. V

GEORGE F. HORTON.

